Ground Engaging Tool System

ABSTRACT

A ground engaging tool system comprises a ground engaging tool such as a tip, an adapter mounted to or part of a work tool, and a rotating lock member. The ground engaging tool is attached to the adapter, and a post portion of the adapter slides into a slot provided on the lock. The lock is rotated so that the entrance to the slot is blocked and the post cannot slide out of the slot. The lock in this position is in a locking position, and the retention of the post in the slot of the lock retains the ground engaging tool to the adapter.

This application is a continuation of U.S. nonprovisional patentapplication Ser. No. 11/840,144, filed on Aug. 16, 2007, which in turnclaims the benefit of U.S. provisional patent application No. 60/822,634filed Aug. 16, 2006

TECHNICAL FIELD

The field of this invention is ground engaging tools, and morespecifically systems for retaining ground engaging tools on buckets,blades, and other work tools.

BACKGROUND

Many construction and mining machines, such as excavators, wheelloaders, hydraulic mining shovels, cable shovels, bucket wheels, anddraglines make use of buckets to dig material out of the earth. Thebuckets can be subjected to extreme wear from the abrasion and impactsexperienced during digging. Other construction and mining machines, suchas bulldozers, also include blades or other tools that are used to movematerial such as soil and rock. These blades and other tools can also besubjected to extreme wear through abrasion and other wear mechanisms.

Buckets and blades and other earth-working tools can be protectedagainst wear by including ground engaging tools (GET). GET is typicallyfashioned as teeth, edge protectors, and other components which areattached to the bucket or blade in the area where the most damagingabrasion and impacts occur. For example, the cutting edge of a bucketcan be protected with edge protectors that wrap around and protect theedge.

Thus, one purpose of the GET is to serve as wear material and absorbwear that would otherwise occur on the bucket, blade, or other tool. TheGET can be removed when it has been worn and replaced with new GET at areasonable cost to continue to protect the bucket. Large buckets fordraglines and hydraulic shovels can cost a considerable amount, soprotecting them against wear and the need for early replacement isimportant. It is more economical to wear out and replace the GET than towear out and replace an entire bucket.

In addition to the purpose of protecting against wear, another purposeof the GET may be to provide more effective digging. A tooth mounted onthe edge of a bucket, for example, may allow the bucket to penetrateinto the soil or rock and dig more effectively with less effort.

Many systems have been proposed and used for removably attaching the GETto buckets and other tools. These systems typically provide a pin orother fastener which holds the GET onto the bucket or other tool. Manyproblems or disadvantages exist with these known systems. For example,in some conditions the pins can become stuck inside the GET because ofrust or because other material gets in the space surrounding the pinsand causes binding or adhesion. As another example of a disadvantage ofsome known attachment systems, some require a hammer to drive in the pinor other fastener. On large GET systems, the hammer required to drive inthe pin may likewise be very large, and swinging such a large hammer indifficult field conditions can be objectionable for the technician.

The pin or other fastener must be very secure and reliable and notpermit the GET to fall off of the bucket or other work tool, even whenthe GET is worn extensively. If the GET falls off of the bucket orblade, it could be fed into a crusher or other processing machine andcause damage. Other problems may also occur if the GET inadvertentlyfalls off the bucket, including extensive wear of the exposed area ofthe bucket left unprotected when the GET fell off which might occurbefore the problem is detected and repaired. The prior art GET attachingsystems have not always held the GET to the bucket or other work toolwith adequate reliability.

In general, the prior art GET attaching systems leave room forimprovement. This invention provides improvements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-3 are schematic assembly views representing a GET attachmentsystem according to the principles of the invention. In FIG. 1, a post(normally attached to the adapter) is sliding into the slot of a lock,the lock being engaged with the tip. In FIG. 2, the post is engaged inthe slot, and in FIG. 3, the lock is rotated to the locking position.

FIG. 4 is a pictorial view of a tip, locking retainer, and lock of afirst embodiment, and the manner in which they may be assembledtogether.

FIG. 5 is a pictorial view of the tip, retainer bushing, and lockassembly according to the first embodiment of FIG. 4, with the lock inan unlocking position.

FIG. 6 is a side view of the assembly of FIG. 5.

FIG. 7 is a rear view of the assembly of FIG. 5.

FIG. 8 is sectional view of the assembly of FIG. 5, taken along plane8-8 indicated in FIG. 7.

FIG. 9 is a pictorial view of the tip, retainer bushing, and lockassembly according to the first embodiment of FIG. 4, with the lock in alocking position.

FIG. 10 is a side view of the assembly of FIG. 9.

FIG. 11 is a rear view of the assembly of FIG. 9.

FIG. 12 is sectional view of the assembly of FIG. 9, taken along plane12-12 indicated in FIG. 11.

FIG. 13 is a pictorial view of an adapter according to the firstembodiment.

FIG. 14 is an assembly view of the tip, retainer bushing, lock, andadapter assembly according to the first embodiment.

FIG. 15 is a sectional view of the assembly of FIG. 14, taken alongplane 15-15 of FIG. 14, with the lock in a locking position.

FIG. 16 is a sectional view of the assembly of FIG. 14, taken alongplane 15-15 of FIG. 14, with the lock in an unlocking position.

FIG. 17 is a sectional view of the adapter of FIG. 15 (the tip, retainerbushing, and lock have been removed in this view).

FIG. 18 is a sectional view of the tip, lock, and retainer bushing ofFIG. 15 (the adapter has been removed in this view).

FIG. 19 is a sectional view of the tip and retainer bushing of FIG. 15(the adapter and lock have been removed in this view).

FIG. 20 is a sectional view of the tip of FIG. 15 (the adapter, lock,and retainer bushing have been removed in this view).

FIGS. 21A-E are views of the lock of the first embodiment.

FIGS. 22A-E are view of the retainer bushing of the first embodiment.

DETAILED DESCRIPTION

FIGS. 1-22 illustrate embodiments and schematic concepts for GETattachment systems according to the invention. The purpose of thesefigures is only to aid in explaining the principles of the invention.Thus, the figures should not be considered as limiting the scope of theinvention to the embodiments and schematic concepts shown therein. Otherembodiments of GET attachment systems may be created which follow theprinciples of the invention as taught herein, and these otherembodiments are intended to be included within the scope of patentprotection.

FIGS. 1-3 demonstrate schematically how the GET attachment system holdsthe GET onto the bucket or blade, and how it locks and unlocks.

With reference first to FIG. 1, a post, or pin, 10 is illustrated. Thepost 10 may be connected or associated with a bucket, blade, or otherwork tool. In FIG. 1, only a portion of the post 10 is shown. Theportion of post 10 that connects with the bucket, blade, or other worktool has been removed from this view for the purpose of illustrating themanner in which the GET attachment system interacts with the post. Alock 20 is also illustrated. The lock 20 includes a slot 21 formedtherein for accepting a portion of post 10. Lock 20 is received in alock cavity 41 of a tip 40. The lock cavity 41 is shaped to allow thelock 20 to fit therein, and also to allow lock 20 to rotate relative totip 40. Lock 20 may be placed in lock cavity 41 directly, or a retainerbushing 30 may be disposed around a portion of lock 20, and disposedbetween the lock 20 and lock cavity 41. The purpose and benefits of theoptional retainer bushing 30 will be explained in greater detailhereinafter.

With reference now to FIG. 2, a pictorial view is shown of the post 10positioned inside of the slot 21 of lock 20. In order for the post 10 toenter slot 21, it may be required to pass through a slot 42 formed intip 40. This will occur typically by sliding the tip 40 and lock 20 ontoa portion of the bucket, blade, or work tool and onto post 10. Forexample, a bucket may include an adapter with an adapter nose that fitsinside of pocket 43 formed in tip 40, in a manner well known in thisindustry. The post 10 may be connected with the adapter. The post 10will slide first through slot 42, then into slot 21. Slot 21 need not bea through slot as illustrated, but could also be a blind slot similar toslot 42. With the lock 20 rotated to the orientation relative to the tip40 that is depicted in FIG. 2, the post 10 can freely slide into and outof the slot 21. This first position of the lock 20 is the unlockingposition.

With reference now to FIG. 3, the lock 20 has been rotated, in this case180 degrees, to a new orientation relative to the tip 40. This secondposition of the lock 20 is the locking position. In the lockingposition, the opening of slot 21 is no longer aligned with slot 42. Lock20 includes a C-shaped portion formed by a rear leg 22 joining togethera top leg 23 and an opposite bottom leg 24. Slot 21 is located betweenthe opposing top leg 23 and bottom leg 24. In the locking position oflock 20 shown in FIG. 3, rear leg 22 blocks the post 10 from exiting theslot 21 and sliding out through the slot 42. Thus, with the lock 20rotated to the locking position, the tip 40 is locked onto the post 10and the bucket, blade, or work tool to which the post 10 is connected.

FIGS. 1-3 illustrate schematically the basic functioning of the GETattachment system. The system may be adapted to many differentapplications. For example, the system may be used to attach manydifferent kinds of cutting edges to blades, tips, edge protectors, sidecutters and other accessories to buckets, tips to compactor wheels, etc.Many variations of the basic designs shown in FIGS. 1-3 are alsopossible. Those of ordinary skill in this field will be able to adaptthe basic parts to suit a particular need in a given application. Forexample, the shapes of post 10, lock 20, and slot 21 may vary widely,according to particular needs in a given application. As anotherexample, tip 40 may be more broadly defined as a first element 40 whichcould take the form of a tip for a bucket or ripper, or could take theform of an edge protector, sidebar protector, or other forms of GET. Asanother example, the structure that connects to post 10 may be broadlydefined as a second element, and may take the form of an adapterpermanently or removably attached to a bucket, or may take the form of abucket sidebar or base edge, or any other portion of a work tool such towhich it is desired to attach GET. As another example, the way in whichthe lock 20 is rotated may vary according to needs of the application.The lock 20 may include a portion that can be rotated by a tool placedthrough a bore in tip 40. Or, the end of post 10 may be modified so itfits in the slot 21 in a way that the post 10 and lock 20 rotatetogether. Then a bore in tip 40 may provide access to the end of post10, and the post 10 could be rotated causing a corresponding rotation oflock 20. Many different designs are possible while still utilizing thebasic principles of this attachment system.

FIGS. 4-22 illustrate a first embodiment of a GET attachment systemaccording to these principles. The first embodiment is also exemplary ofmany additional, optional features which may be incorporated to satisfyparticular needs or provide optional benefits.

With reference first to FIG. 4, a lock 200, retainer bushing 300, andtip 400 are illustrated. The tip 400 may be manufactured from steel orany other suitable material. The exterior of the tip 400 featuressurfaces designed to contact soil and rock, and absorb or resist theabrasive and impact forces. The exterior surfaces can form a relativelysharp front edge 401 in order to permit the tip 400 to penetrate intothe soil or rock and facilitate digging. The tip 400 may also include atop portion 402, a bottom portion 403, and side portions 404. In thedesign shown in FIG. 4, the top portion 402, bottom portion 403, andside portions 404 meet together and form the front edge 401. The topportion 402, bottom portion 403, and side portions 404 also form aninterior adapter receiving cavity 430. The adapter receiving cavity 430is shaped to receive the nose portion of an adapter (see FIG. 13). Theadapter receiving cavity 430 opens out of the tip 400 through a rearportion or surface 405. Rear surface is bordered by the top portion 402,bottom portion 403, and side portions 404. Several eyelets 406 may beattached to any of the tip exterior surfaces to facilitate lifting andpositioning the tip 400 during installation.

The tip 400 also includes a slot 410 positioned adjacent a lock cavity420. Lock cavity 420 is sized to receive the lock 200, and optionallythe retainer bushing 300 therein. Lock cavity 420 also includes a lockopening 421 (FIG. 6) which leads from the lock cavity 420 to theexterior of the tip 400. Slot 410 includes side walls 411 and a bottomwall 412. Side walls 411 extend away from the adapter receiving cavity430 towards the bottom wall 412 so that bottom wall 412 is recessedbelow the surrounding surface of the adapter receiving cavity 430 andslot 410 is generally contained within a side portion 404. Side walls411 and bottom wall 412 may define a plane of symmetry which extendsparallel to the slot's longitudinal axis. The longitudinal axis of slot410 runs from the rear surface 405 towards the lock cavity 420. Thelongitudinal axis of slot 410 may also run parallel to the direction ofmovement of the tip 400 relative to the worktool when the tip isinserted on or removed therefrom (see arrow A, FIG. 16). The slot 410opens up to the rear surface 405 on one end, and to the lock cavity 420on the other opposite end.

Retainer bushing 300 can be formed from plastic or any other suitablematerial. If formed from plastic, it may be desirable to produce itthrough injection molding. Lock 200 can be formed from steel or anyother suitable material. If both tip 400 and lock 200 are formed ofsteel, then having a plastic retainer bushing 300 creates certainbenefits. First, a plastic retainer bushing can prevent metal-to-metalcontact, and the wear mechanisms commonly exhibited with such contact.Second, a plastic retainer bushing can help prevent corrosion or otherprocesses between the tip and the lock which, over time, could cause thelock to seize in the tip and make the lock difficult to rotate. If thelock cannot be easily rotated, then the tip removal from the work toolis more difficult. Third, a plastic retainer bushing which can deflectmore easily than steel can allow a retaining relationship between thetip and the retainer bushing, and the lock and the retainer bushing, asdescribed more fully below. Thus, the choice of plastic to form theretainer bushing 300 can be particularly advantageous.

With reference to FIG. 4 and FIGS. 22A-E, the retainer bushing 300includes a slot 310 formed in a substantially circumferential skirtportion 320. The skirt portion 320 may be conically shaped. Attached tothe narrower end of the skirt portion 320 is a head portion 330. Headportion 330 includes an opening 331, and a flexible tab 332. Tab 332flexion is promoted by a relief hole 333 formed in the head portion 330.

With reference to FIG. 4 and FIGS. 21A-E, the lock 200 includes a slot210. Slot 210 is formed in a C-shaped portion 220 of the lock 200.C-shaped portion 220 includes a rear leg 221, top leg 222, and bottomleg 223. Slot 210 is interposed between top leg 222 and bottom leg 223.On top of C-shaped portion 220 is a head portion 230. Head portion 230includes two detents 231, 232, formed therein, and an annular surface233 positioned between the detents 231, 232. A stopping tab 234 is alsoformed in the head portion 230. Head portion also includes a toolinterface 235.

FIGS. 5-8 show views of the lock 200 assembled into the retainer bushing300, and the retainer bushing 300 assembled into the tip 400. The lock200 is rotated to its first position, or unlocking position in each ofthese views. While the lock 200 is in the unlocking position, an adapteror portion of a work tool can be inserted into the adapter receivingcavity 430, and a post or other portion associated with the adapter willsimultaneously slide through slot 410, slot 310, and into slot 210.

FIG. 6 is a side view which shows retainer bushing 300 and lock 200projecting through lock opening 421 of tip 400. Tool interface 235 isaccessible by an appropriate tool to help rotate lock 200 relative toretainer bushing 300 and tip 400. Any type of suitable tool and toolinterface may be used. Preferably, the tool includes a male portion, andthe tool interface 235 includes a female portion.

In the unlocking position, tab 332 rests in detent 232. As lock 200 isrotated relative to retainer bushing 300, tab 332 flexes and comes outof detent 232. FIGS. 9-12 show the lock 200 rotated to its secondposition, or locking position. In the locking position, tab 332 rests indetent 231. Further rotation of lock 200 relative to retainer bushing300 is prevented by stopping tab 234 contacting the head portion 330 ofretainer bushing 300. Likewise, when the lock is rotated back to itsunlocking position, stopping tab 234 will contact head portion 330 whentab 332 enters detent 231. This detent and stop system gives techniciansa very good tactile feel for when the lock 200 has been turned to eitherits unlocking or locking position. In part the good tactile feel willcome from the retainer bushing 300 being made from plastic and tab 332being flexible enough to permit easy rotation, while still providingenough holding power against detents 231, 232 to hold lock 200 in itsunlocking or locking position. Movement of the lock 200 from its lockingto unlocking position does not require use of a hammer or other tools asis common with many types of pin retention systems for GET. Hammerlesssystems are increasingly preferred by technicians.

When the lock 200 is assembled into the retainer bushing 300, structureson each help positively hold the two together. Skirt portion 320 ofretainer bushing 300 defines an internal annular surface 340. Lock 200includes an external annular surface 240. Internal annular surface 340rides against external annular surface 240 when lock 200 rotatesrelative to retainer bushing 300. In this embodiment, the annularsurfaces 240, 340 are also tapered, resulting in an overall conicalshape. Internal annular surface includes ribs 341 formed thereon whichextend in a substantially circumferential direction. When lock 200 ispositioned inside of retainer bushing 300, the ribs 341 interfere withexternal annular surface 240. In order to fit lock 200 inside retainerbushing 300, adequate force must be applied to deflect retainer bushing300 so ribs 341 can move past external annular surface 240. Once ribs341 move past external annular surface 240, ribs 341 and the retainerbushing 300 can return to a more natural, non-deflected position. Ribs341 will ride against a bottom surface 224 of C-shaped portion 230,preventing lock 200 from unintentionally slipping out of retainerbushing 300. Lock 200 is able to rotate inside of and relative toretainer bushing 300.

Likewise, when the retainer bushing 300 is assembled into lock cavity420 of tip 400, structures on each help positively hold the twotogether. Skirt portion 320 of retainer bushing 300 defines an externalsurface 350. External surface 350 includes a rib 351 formed in asubstantially circumferential direction. A complementary slot 422 (FIG.4) is formed in the lock cavity 420 of tip 400. When retainer bushing300 is assembled into lock cavity 420, the rib 351 first interferes withlock cavity 420. In order to fit retainer bushing 300 inside of lockcavity 420, adequate force must be applied to deflect retainer bushing300 so that rib 351 slides past the lock cavity 420 surfaces with whichit interferes, until rib 351 snaps into slot 422. Retainer bushing 300cannot rotate relative to tip 400 once installed into the lock cavity420. The fit of rib 351 into slot 422 prevents rotation. Also, the lockopening 421 is non-circular. The part of head portion 330 of retainerbushing 300 which fits into the lock opening 421 is also non-circular.The fit of the head portion 330 into the lock opening 421 and thenon-circular shape of each also prevents the retainer bushing 300 fromrotating relative to the tip 400.

Holding together, under normal conditions, the lock 200 to the retainerbushing 300, and the retainer bushing 300 to the tip 400, has severaladvantages. First, during shipping of a replacement tip assembly(including tip 400, retainer bushing 300, and lock 200) to a jobsite,all three components stay together without becoming mixed up or lost.Second, during installation, it is simple to keep all three componentsin position relative to one another while the tip assembly is slid ontoan adapter or other work tool. The installation may sometimes beconducted in challenging field conditions, including mud and snow. Beingable to keep all the components together prevents them from beingdropped into the mud and snow and becoming lost. Further, a technicianwho may be wearing protective gloves will not be required to handle thelock 200 and retainer bushing 300 which are smaller components and maynot be as easily grasped and manipulated. In general, this featuregreatly enhances the ease and speed of installation.

With reference now to FIGS. 13-17, an adapter 100 is illustrated whichmay be used with the tip 400, retainer bushing 300, and lock 200.Adapter 100 includes a nose portion 110. Nose portion 110 is shaped tofit inside of adapter receiving cavity 430 of tip 400. The shape of noseportion 110, and the complementary shape of adapter receiving cavity430, may be selected to suit any particular need or application. Severaldifferent shapes have been used in prior GET systems, and any suitablegeneral shape could be selected. The nose portion 110 includes oppositesloping top and bottom surfaces 111, 112 which slope towards one anotherand toward two opposite flat surfaces 113, 114, and a flat front surface115. The nose portion 110 also includes two opposite side surfaces 116,117.

Opposite the nose portion 110 is the rear portion 118 which may includea second adapter receiving cavity 119. In this embodiment, as is knownin this field, adapter 100 is configured to be received onto a secondadapter that is mounted to a work tool. The second adapter (not shown)would include a nose portion that complements the second adapterreceiving cavity 119.

On side surface 117 is formed a post 120. Post 120 in this embodiment isof a generally conical shape. Other shapes could be selected to suitother designs. Post 120 includes a substantially conical surface 121,and a substantially flat end surface 122. As seen in FIG. 17, conicalsurface 121 defines a central axis A of the cone shape. Conical surface121 is formed at a taper angle β of approximately 10-30 degrees, andmore preferably about 20 degrees. The adapter 100 defines a plane ofsymmetry B as illustrated in FIG. 17 (the adapter 100 is generallysymmetrical about the plane B, discounting the post 120 and relatedstructure). The angle α between plane B and axis A is approximately65-85 degrees, and more preferably about 75 degrees.

Adapter 100 also includes a half-annular-shaped cut 130 into the sidesurface 117 immediately adjacent and behind (in the direction of rearportion 118) the post 120. Immediately adjacent and behind (in thedirection of rear portion 118), the adapter 100 also includes a rail 140raised above the side surface 117. Rail 140 is generally sized andshaped to match slot 410 of tip 400.

FIGS. 15-16 show sectional views of the tip 400, bushing retainer 300,and lock 200 mounted to adapter 100. FIG. 15 shows the lock 200 rotatedto its locking position so the tip 400 cannot be removed from adapter100. FIG. 16 shows the lock 200 rotated to its unlocking position sothat the tip 400 can slide in the direction of arrow A off of adapter100. In each view, rail 140 is shown positioned in slot 410 where isserves to block dirt and other debris from entering into slot 410. Ifdirt and other debris were allowed to enter slot 410, they may becomeimpacted and make removal of the tip 400 difficult because post 120 mustslide through slot 410 when the tip is removed.

With central axis A of post 120 positioned at an angle with respect tothe plane of symmetry B, FIG. 15 shows that the rearward most portion ofconical surface 121 which contacts lock 200 in the locking position isat an angle near perpendicular to the direction of force of the tip 400being pulled straight off of adapter 100 (as indicated by arrow A). Thishelps prevent the force of the tip 400 being pulled off of adapter 100from twisting the tip 400, deflecting out of position lock 200 andcausing the lock 200 to slip off of post 120 in a failure. Positioningthe post 120 in this manner also minimizes the magnitude of the reactionforce that will tend to push lock 200 into the lock cavity 420. Theminimized reaction forces can be counteracted by compressive forces inthe tip 400.

FIG. 19 shows that when positioned in tip 400, retainer bushing 300 hasa bottom surface 334 set at an angle γ relative to the plane of symmetryB of tip 400 of approximately 5 to 25 degrees, and most preferably 15degrees. Head portion 230 of lock 200 has a bearing surface 236 thatabuts and slides on bottom surface 334 of retainer bushing 300. Withbottom surface 334 set at this angle, the lock 200 rotates between itslocking and unlocking position about an axis approximately parallel tocentral axis A of the post 120.

INDUSTRIAL APPLICABILITY

The foregoing ground engaging tool system may be used in industry toprovide protection and improved digging ability for buckets, blades andother work tools on construction and mining machinery, and other typesof machinery.

1-8. (canceled)
 9. A retainer system, comprising: a lock including: aC-shaped portion defining a slot; and a head portion attached to theC-shaped portion and having a first detent, a second detent, an annularsurface extending between the first detent and the second detent, and atool interface.
 10. The retainer system of claim 9, in which theC-shaped portion of the lock comprises a bottom leg, a rear leg, and atop leg.
 11. The retainer system of claim 10, in which the slot of thelock is interposed between the top leg and the bottom leg.
 12. Theretainer system of claim 9, further comprising a retainer bushing havinga skirt portion formed with an internal surface configured to rotatablyreceive an external surface of the C-shaped portion of the lock, and inwhich the lock is rotatable relative to the retainer bushing.
 13. Theretainer system of claim 12, in which the skirt portion of the retainerbushing includes a slot, and in which the slot of the skirt portion ofthe retainer bushing is aligned with the slot of the C-shaped portion ofthe lock when the lock is in an unlocking position.
 14. The retainersystem of claim 12, in which the interior surface of the skirt portionof the retainer bushing has a conical shape.
 15. The retainer system ofclaim 12, in which the retainer bushing further includes a tabconfigured to selectively engage the first detent and the second detent.16. The retainer system of claim 15, in which the retainer bushingincludes a head portion attached to the skirt portion, and in which thetab is provided on the head portion of the retainer bushing.
 17. Theretainer system of claim 16, in which the head portion of the lockfurther comprises a stopping tab configured to engage the head portionof the retainer bushing, wherein the stopping tab is located to engagethe head portion of the retainer bushing when rotated in a firstdirection, thereby to prevent rotation of the lock past an unlockingposition, and to engage the head portion of the retainer bushing whenrotated in a second, opposite direction, thereby to prevent rotation ofthe lock past a locking position.
 18. The retainer system of claim 16,in which the head portion of the lock includes a bearing surface and thehead portion of the retainer bushing includes a bottom surfaceconfigured to rotatably engage the bearing surface.
 19. The retainersystem of claim 18, including a body defining a plane of symmetry, inwhich the bottom surface of the retainer bushing is set at an angle γrelative to the plane of symmetry of approximately 5 to 25 degrees. 20.The retainer system of claim 16, in which the head portion of theretainer bushing includes an opening sized to receive the head portionof the lock.
 21. The retainer system of claim 15, in which the tabincludes a relief hole.
 22. The retainer system of claim 12, in whichthe skirt portion of the retainer bushing includes an exterior surfacehaving an annular, circumferential rib.
 23. The retainer system of claim12, in which the C-shaped portion of the lock includes a bottom surface,and in which the internal surface of the skirt portion of the retainerbushing includes two circumferential ribs positioned to engage thebottom surface of the C-shaped portion of the lock when the retainerbushing and lock are assembled.
 24. A retainer system for a groundengaging tool, the retainer system comprising: a lock including: aC-shaped portion having a bottom leg, a rear leg, and a top leg, inwhich a slot is interposed between the top leg and the bottom leg; and ahead portion attached to the C-shaped portion and having a first detent,a second detent, an annular surface extending between the first detentand the second detent, and a tool interface; and a tab configured toselectively engage the first detent and the second detent; wherein thelock is rotatable between an unlocking position, in which the tabengages the first detent, and a locking position, in which the tabengages the second detent.
 25. The retainer system of claim 24, furthercomprising a retainer bushing having a skirt portion formed with aninternal surface configured to rotatably receive an external surface ofthe C-shaped portion of the lock, in which the lock is rotatablerelative to the retainer bushing, and in which the tab is formed on theretainer bushing.
 26. A retainer system for a ground engaging tool, theretainer system comprising: a lock having a C-shaped portion defining aslot, and a head portion attached to the C-shaped portion and having afirst detent, a second detent, an annular surface extending between thefirst detent and the second detent, and a tool interface; and a retainerbushing including a skirt portion formed with an internal surfaceconfigured to rotatably receive an external surface of the C-shapedportion, the retainer bushing including a tab configured to selectivelyengage the first detent and the second detent; wherein the lock isrotatable relative to the retainer bushing between an unlockingposition, in which the tab engages the first detent, and a lockingposition, in which the tab engages the second detent.
 27. The retainersystem of claim 26, in which the skirt portion of the retainer bushingincludes a slot, and in which the slot of the skirt portion of theretainer bushing is aligned with the slot of the C-shaped portion of thelock when the lock is in the unlocking position.
 28. The retainer systemof claim 27, in which the head portion of the lock further comprises astopping tab configured to engage the head portion of the retainerbushing, wherein the stopping tab is located to engage the head portionof the retainer bushing when rotated in a first direction, thereby toprevent rotation of the lock past an unlocking position, and to engagethe head portion of the retainer bushing when rotated in a second,opposite direction, thereby to prevent rotation of the lock past alocking position.